Os Odontoideum in Children: Treatment Outcomes and Neurological Risk Factors

Os odontoideum: database analysis of 260 patients regarding etiology, associated abnormalities, and literature review

Introduction

Since the first description of os odontoideum in 1886, its origin has been debated. Numerous case series and reports show both a possible congenital origin and origin from the secondary to craniovertebral junction (CVJ) trauma. We conducted a detailed analysis of 260 surgically treated cases to document the initial symptoms, age groups, radiographic findings, and associated abnormalities, aiming to enhance the confirmation of the etiology. A literature search (1970-2022) was performed to correlate our findings.

Methods and materials

A total of 260 patients underwent surgical management of a referral database of 520 cases (1978-2022). All patients were examined by plain radiography and myelotomography as needed until 1984, and since then, CT and MRI have been employed. History of early childhood (aged below 6 years) CVJ trauma was investigated, including obtaining emergency department's initial radiographs from the referral and subsequent follow-up. Associated radiographic and systemic abnormalities were noted, and the atlas development was followed.

Results

The age of the patients ranged from 4 to 68 years, mostly between 10 and 20 years. There were 176 males and 86 females. Orthotopic os odontoideum was identified in 24 patients, and 236 patients had dystopic os odontoideum. Associated abnormalities were found in 94 of 260 patients, with 73 exhibiting syndromic abnormalities and 21 having Chiari I malformation. Two sets of twins had spondyloepiphyseal dysplasia. Of 260 patients, 156 experienced early childhood trauma /. Among these, 54 initially presented with normal radiographs but later demonstrated anterior atlas hypertrophy. In addition, a smaller posterior C1 arch was observed, leading to the development of os odontoideum. Two children had initial CVJ trauma as documented by MRI, with subsequent classical findings of os odontoideum and atlas changes. Syndromic patients had an earlier presentation. The literature reviewed confirms the multifactorial etiology.

Conclusions

The early presentation and associated abnormalities (such as Down syndrome, Klippel-Feil syndrome, Chiari I malformation, spondyloepiphyseal dysplasia, Morquio syndrome, and others) along with case reports documenting familial, hereditary, and twin presentations strongly support a congenital origin. Likewise, surgical complications are more prevalent in syndromic patients (40%) compared to 15% in other cases, as reported in the literature. The documentation of normal odontoid in early childhood trauma cases followed by the later development of os odontoideum provides evidence supporting trauma as an etiological factor. This process also involves vascular changes in both the atlas and the formation of os odontoideum. Associated abnormalities exhibit an earlier presentation and are only seen in cases with a non-traumatic origin.

Vertebral Artery Dissection in the Setting of Unstable Os Odontoideum: A Case Report

CASE

A healthy 5-year-old boy presented with a gradual onset of headaches and acute global right-sided weakness over 10 days. The work-up revealed unstable os odontoideum leading to multiple posterior circulation infarcts with vertebral artery dissection. He underwent antiplatelet therapy, cervical collar immobilization, and delayed occiput to C2 posterior spinal fusion and instrumentation with iliac crest autograft. At 2-year follow-up, the patient had a solid fusion mass, appropriate cervical alignment, and was without neurologic sequelae.

CONCLUSION

This case adds to a sparse body of literature in the management of vertebral artery dissection with vertebrobasilar insufficiency secondary to unstable os odontoideum.

Congenital Cervical Spinal Deformities

Malformations of the cervical spine are a challenge in pediatric orthopedic surgery since the treatment options are limited. These congenital anomalies are often syndrome-related and have multiple repercussions on the function and statics of the cervical spine in all three planes. They are related to developmental abnormalities during the somite segmentation that occurs during the third week of embryonic development. Successful somitogenesis requires proper functioning of a clock regulated by complex signaling pathways that guide the steps needed to form the future spine. There is no specific classification for vertebral malformations at the cervical level. To characterize the progressive nature of a malformation, one must use general classifications. In the specific case of Klippel-Feil syndrome, these malformations can affect several vertebral levels in a continuous or discontinuous manner, but also the vertebral body and vertebral arch in a variable way. Thus, establishing a reliable prognosis in the coronal and sagittal planes is a complex undertaking. While technical mastery of certain osteotomy procedures has led to advances in the surgical treatment of rigid deformities of the cervical spine, the indications are still very rare. Nevertheless, the procedure has become safer and more accurate because of technical aids such as surgical navigation, robotics and 3D printed models or patient-specific guides. Occipitocervical transitional anomalies have embryological specificities that can explain the bony malformations seen at this level. However, most are rare, and the main concern is identifying any instability that justifies surgical stabilization. The presence of a cervical spine anomaly should trigger the search for occipitocervical instability and vice-versa.

Os odontoideum: A comprehensive review

Os odontoideum (OO) is a rare craniocervical anomaly that is characterized by a round ossicle separated from the C2 vertebral body. With a controversial etiology and unknown prevalence in the population, OO may be asymptomatic or present in patients with myelopathic and neurological symptoms. In this literature review, we aimed to investigate epidemiology, embryology, pathophysiology, clinical presentation, and the role of diagnostic radiography in OO. By providing an overview of different management strategies, surgical complications, and postoperative considerations for OO, our findings may guide neurosurgeons in providing proper diagnosis and treatment for OO patients. A literature review was conducted using the PubMed, EMBASE, and Scopus databases. A search using the query “os odontoideum” yielded 4319 results, of which 112 articles were chosen and analyzed for insights on factors such as etiology, clinical presentation, and management of OO. The presentation of OO varies widely from asymptomatic cases to severe neurological deficits. Asymptomatic patients can be managed either conservatively or surgically, while symptomatic patients should undergo operative stabilization. Although multiple studies show different techniques for surgical management involving posterior fusion, the diversity of such cases illustrates how treatment must be tailored to the individual patient to prevent complications. Conflicting studies and the paucity of current literature on OO highlight poor comprehension of the condition. Further understanding of the natural history of OO is critical to form evidence-based guidelines for the management of OO patients. More large-center studies are thus needed to promote accurate management of OO patients with optimal outcomes.

A retrospective study of incidental findings occurring in a consecutive case series of lateral cephalograms of 12- to 20-year-old patients referred for routine orthodontic treatment

Purpose

Lateral cephalograms of orthodontic patients may contain incidental findings that could potentially lead to harm.

Materials and Methods

The lateral cephalograms of 1765 consecutive 12- to 20-year-old patients, being considered for routine orthodontic treatment, were retrospectively reviewed. These patients were considered normal, because no abnormalities were found either in their medical history or on their clinical examination.

Results

The overall prevalence of incidental findings was 18.8%, of which 10.3% were ponticulus posticus and 4.2% were bridging of the sella turcica. Although occipital spurs and ponticulus posticus were more prevalent in males, the size of the sella turcicas did not differ between sexes. Of the 1156 patients completing treatment about 2 years later, only one lateral cephalogram displayed progression of the ponticulus posticus in that time.

Conclusion

The prevalence of incidental findings on lateral cephalograms of otherwise normal orthodontic 12- to 20-year-old patients was almost a fifth, of which ponticulus posticus, vertebral fusion, and enlarged parietal foramina were clinically significant.

Anatomical Study on the Safety of Anterior Cervical Craniovertebral Fusion with Clival Screw Placement in Children Aged 1-6 Years

Objective

This study aimed to investigate the safety of clival screw placement in children aged 1–6 years.

Methods

The cranial computed tomography data of 92 children aged 1–6 years were divided into three groups, according to age, for three-dimensional reconstruction. Three clival screw placement points were defined: (1) median point A at the middle and upper third of the tripartite distance from the spheno-occipital synchondrosis to the base of the skull; (2, 3) critical points B and C on the horizontal line with point A, where the screw placement passage was parallel to the sagittal plane. Parameters such as the passage length and angle were measured for horizontal, vertical facial, and extreme screw placement.

Results

The length parameters of the clival screw placement increased with age, and the screw passage length was the shortest for the vertical facial type in each age group. There were significant differences in all three groups between the length of screw placement in the vertical bone surface, the length of screw placement in the horizontal direction, and the length of screw placement on the limit at points A, B, and C (P < 0.05); the length of screw placement on the vertical bone surface was the shortest. There was no significant difference between the horizontal screw length at point A and the extreme screw length (P > 0.05). The difference between the horizontal screw length and the extreme screw length in the groups aged 1–2 years and 5–6 years was statistically significant (P < 0.05), and the horizontal screw length was longer.

Conclusion

The cranial slope of children aged 1–6 years has the morphological basis for the placement of 3.5 mm screws, and each placement point has a safe angle range for screw placement.

Repeat Pediatric Trisomy 21 Radiographic Exam: Does Atlantoaxial Instability Develop Over Time?

BACKGROUND

Atlantoaxial instability (AAI) is common in pediatric patients with Trisomy 21 and can lead to spinal cord injury during sports, trauma, or anesthetized neck manipulation. Children with Trisomy 21 therefore commonly undergo radiographic cervical spine screening, but recommendations on age and timing vary. The purpose of this study was to determine if instability develops over time.

METHODS

We performed a retrospective review for all pediatric Trisomy 21 patients receiving at least 2 cervical spine radiographic series between 2008 and 2020 at our institution. Atlantodens interval (ADI) and space available for the cord at C1 (SAC) were measured; bony abnormalities such as os odontoidium, and age and time between radiographs were noted. AAI was determined by ADI ≥6 mm or SAC ≤14 mm based on our groups' prior study. Those who developed instability were compared with those who did not.

RESULTS

A total of 437 cervical spine radiographic series from 192 patients were evaluated, with 160 included. Mean age at first radiograph was 7.4±4.4 years, average ADI was 3.1 mm (±1.2), and SAC was 18.1 mm (±2.6). The average time between first and last radiographs was 4.3 years (±1.8), with average final ADI 3.2 mm (±1.4) and SAC 18.9 mm (±2.9). Seven patients (4%) had instability: 4 were unstable on their initial studies and 3 (1.6%) on subsequent imaging. Os odontoideum was found in 5 (71%) unstable spines and 3 (2%) stable spines (P<0.0001); only 1 patient that became unstable on subsequent radiograph did not have an os. There was no specific age cut-off or surveillance time period after which one could be determined no longer at risk.

CONCLUSIONS

Trisomy 21 patients have a 4.4% overall rate of AAI in our series with a 1.6% rate of progression to instability over ∼4 years. Given this nearly 1 in 23 risk of instability, we recommend initial surveillance radiograph for all children over 3 years with Trisomy 21; repeat asymptomatic surveillance should continue in those with os odontoideum given their high instability risk.

LEVEL OF EVIDENCE

Level II-diagnostic study.

The technique of using three-dimensional and multiplanar reformatted computed tomography for preoperative planning in pediatric craniovertebral anomalies

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Surgical planning of pediatric craniovertebral anomalies is requires multiplanar CT reconstructions.

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Screw trajectories can be planned in 4 steps using an open-source DICOM manipulation software.

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This method gives more anatomical information compared to studying conventional PACS images.

Background

Computed tomography (CT) images provided by the radiology department may be inadequate for planning screws for rigid craniovertebral junction (CVJ) instrumentation. Although many recommend using multiplanar reconstruction (MPR) in line with screw trajectories, this is not always available to all surgeons. The current study aims to present a step-by-step workflow for preoperative planning for pediatric CVJ anomalies.

Methods

Twenty-five consecutive children (<12 years) were operated for atlantoaxial instability between 2014 and 2019. Preoperative CT angiograms were transferred to an open-source software called Horos™. The surgeon manipulated images in this viewing software to determine an idealized path of screws. Three-dimensional volume rendering of the pathoanatomy was generated, and anomalies were noted. The surgeon compared the anatomical data obtained using Horos™ with that from the original imaging platform and graded it as; Grade A (substantial new information), Grade B (confirmatory with improved visualization and understanding), Grade C (no added information). The surgeon then executed the surgical plan determined using Horos™.

Results

Surgeries performed were occipitocervical (n = 18, 72%) and atlantoaxial fixation (n = 7, 28%) at a mean age of 7.2 years, with 72% of etiologies being congenital or dysplasias. In 18 (72%) patients, the surgeon noted substantial new information (Grade A) about CVJ anomalies on Horos™ compared to original imaging platform. Concerning planning for fixation anchors, the surgeon graded A in all patients (100%). In 4 (16%) patients, the surgery could not be executed precisely as planned. There were three (12%) complications; VA injury (n = 1), neurological worsening (n = 1), and loss of fixation (n = 1).

Conclusion

In our experience, surgeon-directed imaging manipulation gives more anatomical information compared to studying original imaging planes and should be incorporated in the surgeon's preoperative workup. When image reformatting options are limited, open-source software like Horos™ may offer advantages.

Results of Conservative and Surgical Management in Children with Idiopathic and Nonidiopathic Os Odontoideum

OBJECTIVE

The outcomes of conservative and operative treatment of os odontoideum in children remain unclear. Our objective was to study the outcomes of conservative and surgical treatment of idiopathic os odontoideum in children and compare these outcomes in age- and treatment-matched nonidiopathic children with os odontoideum.

METHODS

A retrospective multicenter review identified 102 children with os odontoideum, of whom 44 were idiopathic with minimum 2-year follow-up. Ten patients were treated conservatively, and 34 underwent spinal arthrodesis. Both groups were matched with nonidiopathic patients by age and type of treatment. Cervical arthrodesis was recommended for patients with increased atlantoaxial distance or reduced space available for the cord in flexion-extension radiographs.

RESULTS

All 20 children undergoing conservative treatment remained asymptomatic during follow-up, but 1 nonidiopathic patient developed cervical instability. The idiopathic group had significantly less severe radiographic cervical instability and less neurologic complications than the nonidiopathic group (P < 0.05 for all comparisons). Thirty-three (97%) patients in the idiopathic group and 32 (94%) patients in the nonidiopathic group (94%) had spinal fusion at final follow-up (P = 0.55). The risk of complications (15% vs. 41%; odds ratio 0.234, 95% confidence interval 0.072-0.757, P = 0.015) and nonunion (6% vs. 24%; odds ratio 0.203, 95% confidence interval 0.040-0.99, P = 0.040) were significantly lower in the idiopathic than in the nonidiopathic group. Idiopathic children undergoing rigid fixation achieved spinal fusion.

CONCLUSIONS

Idiopathic patients with stable atlantoaxial joint at presentation remained asymptomatic and intact during conservative treatment. Idiopathic children with os odontoideum undergoing spinal arthrodesis had significantly fewer complications and nonunion than nonidiopathic children.

LEVEL OF EVIDENCE

III.

Surgical Management of Spinal Disorders in People with Mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are a group of inherited, multisystem, lysosomal storage disorders involving specific lysosomal enzyme deficiencies that result in the accumulation of glycosaminoglycans (GAG) secondary to insufficient degradation within cell lysosomes. GAG accumulation affects both primary bone formation and secondary bone growth, resulting in growth impairment. Typical spinal manifestations in MPS are atlantoaxial instability, thoracolumbar kyphosis/scoliosis, and cervical/lumbar spinal canal stenosis. Spinal disorders and their severity depend on the MPS type and may be related to disease activity. Enzyme replacement therapy or hematopoietic stem cell transplantation has advantages regarding soft tissues; however, these therapeutic modalities are not effective for bone or cartilage and MPS-related bone deformity including the spine. Because spinal disorders show the most serious deterioration among patients with MPS, spinal surgeries are required although they are challenging and associated with high anesthesia-related risks. The aim of this review article is to provide the current comprehensive knowledge of representative spinal disease in MPS and its surgical management, including the related pathology, symptoms, and examinations.